The Vatican's top diplomat in the Holy Land, Archbishop Pietro Sambi, has aroused tensions with Jewish leaders by saying that Pius XII kept silent about the Nazi genocide precisely because he wanted to save Jewish lives.
Archbishop Sambi's defence was immediately ridiculed by Holocaust historians and used as ammunition by ultra-nationalists in Israel calling for a boycott of Pope John Paul II's visit.
It is feared that the nationally broadcast comments, and the bitter reaction they have drawn, could overshadow hopes for reconciliation during the landmark pilgrimage.
Yisrael Gutman, the chief historian at Israel's Yad Vashem Holocaust memorial, said Pius' failure to condemn the Nazis was reprehensible.
"Silence could of course not help," Gutman said. "It could only be interpreted as a lack of interest or as a lack of will to interfere in the Nazi policy ... and murder."
The Vatican has said that Pius had not been informed of the extent of Hitler's purges, which killed six million Jews. In defending Pius' silence, it has cited a 1942 incident in which, after Dutch bishops spoke out against the deportations of Jews, the Nazis sent 300 Catholic converts of Jewish families to Auschwitz.